M. Fosco

Two-stage reimplantation for periprosthetic knee infection: Influence of host health status and infecting microorganism

BACKGROUND Two-stage revision is the gold standard treatment of TKA infection; nevertheless various factors may influence the success rate. The aim of our study was to assess the impact of the number of patient comorbidities together with virulence of infectious organism on prognosis of two-stage revision procedure in chronic peri-prosthetic knee infection; moreover we tried to demonstrate correlation between the presence of positive culture during re-implantation and re-infection rate. METHODS Thirty-eight cases of two-staged revision procedures for infected total knee arthroplasty were prospectively followed. The presence of high virulence microorganisms on the culture result and the number (more than three) of comorbidities were used as major risk factors. All cases were divided into three groups: Group 1 (10 patients without major risk factors), Group 2 (18 patients with only one major risk factor), Group 3 (10 patients with both of major risk factors). RESULTS After a mean follow-up of 65months (range 24-139months), there was infection recurrence in nine cases: four re-infections occurred with the same organism while five patients had re-infection with a different organism. Recurrence was higher in Group 3 (33% of the cases), lower in Group 2 (12% of the cases), whereas no infection occurred in Group 1. Finally in case of positive intraoperative cultures recurrence rate was 83%, whereas when specimens were negative we had only 12.5% of re-infections. CONCLUSIONS Even if standard protocol of two-stage revision has demonstrated good results when treating low-virulence infections or patients without associated risk factors, its application to more challenging condition cannot be assumed. LEVEL OF EVIDENCE Level IV, therapeutic study. See the Guidelines for Authors for a complete description of level of evidence.

Total knee arthroplasty in patients with poliomyelitis

We performed a retrospective chart and radiograph review of 10 patients with a history of poliomyelitis involving a limb that subsequently underwent primary total knee arthroplasty between 2000 and 2008. One posterior stabilized (PS), two condylar constrained (CCK), and seven rotating hinge (RHK) prostheses belonging to the same system were implanted. Eight patients were followed for a minimum of 2 years (mean 4.3 years, range 2 to 8.5 years); one patient required revision for prosthesis infection. The last patient was followed for just six months reporting excellent pain relief, and without complications. American Knee Society Score (AKSS) improved postoperatively in all eight patients with at least 2 years follow-up. The improvement was more marked for the knee score, which increased from a mean of 37 points preoperatively (range 20 to 51) to 75.7 points postoperatively (range 50 to 92); for the functional score the mean increase was only 15.8 points, from a mean of 38.5 points (range 20 to 70) to 54.3 points (range 20 to 80) after the intervention. One patient had a recurrence of the recurvatum deformity after implanting a CCK prosthesis. We found that a rotating hinge prosthesis that allowed hyperextension was suitable treatment for patients with knee osteoarthritis and polio as this compensated for loss of quadriceps power.

Management of Bone Loss in Primary and Revision Knee Replacement Surgery

Total knee arthroplasty (TKA) often deal with bone defect localized in areas corresponding to tibial and femoral articular surfaces, a condition that is often observed in revision knee prosthetic surgery but occasionally in primary arthroplasty of the knee too. Such intraoperative situation, could create a main problem in maintaining proper alignment of the implant components and in establishing sufficient bone stock to achieve a stable boneimplant interface. The surgeon must assess the degree of complexity preoperatively and intraoperatively and have a broad armamentarium available during surgery. Multiple surgical options are available to repair or reconstruct the loss of bone, these include: bone cement, bone grafts, metal augments and custom-made implants. Principles to consider in bone loss management are knee-related (particularly defect size and location, ligament stability, limb alignment) and patient-related (age, body mass index, activity level, life expectancy).

Total Knee Arthroplasty for Post-Traumatic Proximal Tibial Bone Defect: Three Cases Report

Bone stock deficiency in primary as well as in revision total knee arthroplasty (TKA) represents a difficult problem to surgeon with regard to maintaining proper alignment of the implant components and in establishing a stable bone-implant interface. Different surgical procedures are available in these situations, for instances the use of bone cement, prosthetic augments, custom implant, and wire mesh with morsellized bone grafting and structural bone allograft. Structural allograft offers a numerous advantages as easy remodeling and felling cavitary or segmental defects, excellent biocompatibility, bone stock restoration and potential for ligamentous reattachment. In this article we report a short term result of three cases affected by severe segmental medial post/traumatic tibial plateau defect in arthritic knee, for which massive structural allograft reconstruction and primary total knee replacement were carried. The heights of the bone defect were between 27-33 mm and with moderate medio-lateral knee instability. Pre-operative AKS score in three cases was 30, 34 and 51 points consecutively and improved at the last follow-up to 83, 78 and 85 consecutively. No acute or chronic complication was observed. Last radiological exam referred no signs of prosthetic loosening, no secondary resorption of bone graft and well integrated graft to host bone. These results achieved in our similar three cases have confirmed that the structural bone allograft is a successful biological material to restore hemi-condylar segmental tibial bone defect when total knee replacement is indicated.

History of Condylar Total Knee Arthroplasty

The first attempt of treating patients affected by knee osteoarthritis with arthroplasty go back up to the mid-nineteenth century with the use of either a soft tissue interposed within the joint surface or resection of a different amount of bone of both distal femur and proximal tibia. However the concept on which total joint replacement is based can be traced only after the 1880 in Berlin with Thermestocles Gluck who gave a series of lectures describing a system of joint replacement by unit made of ivory. The surgeon believed that these unit could be stabilized in bone with cement made of colophony, pumice and plaster of Paris. The early twentieth saw the return of interposition arthroplasty with the use of autologous tissue or metallic surface and in the 1950s was developed the first surface replacement of the tibia by McKeever (McKeever, 1960). Only during the 1950s and 1960s at last the knee arthroplasty concept diverged into two theories of total joint replacement: the designer focused their effort toward constrained or hinged prosthesis or toward condylar replacement. Condylar replacement knee prosthesis is defined as one where the femoral and tibial loadbearing surface are replaced with non connected artificial components. Work on the design of an implant that resurfaced the distal femur and proximal tibia without any direct mechanical link between the components began at the end of sixties at the Imperial College in London. The original design known as Freeman-Swanson prosthesis consisted of a metal “roller” placed on the distal femur that articulated with a polyethylene tibial tray and requires resection of both cruciate ligaments. In other part of the world were developed different experience which carried out to Polycentric, Geomedic, Duocondylar systems (Fig.1). Even if all of these implants were considered unsatisfactory because of a high percentage of components mobilizations, break of the components and infection the acquired experience permitted the resurfacing prosthesis planning (Insall & Scott, 2001) to occur its successive design phase followed two different ways : the anatomical approach and the functional approach. (Robinson, 2005).

Orthopaedic implant materials and design

Abstract: Knee and hip arthroplasties are designed to replace biological materials that have been damaged, to relieve pain and improve joint function and quality of life. This chapter discusses modern designs of prosthetic components for hip and knee replacement and considers the evolution of prosthetic models in the past. The chapter reviews all biomaterials used in contemporary total joint designs: metals, polymers, ceramics and composites.

Trabecular orientation in the human femur and tibia and the relationship with lower-limb alignment for patients with osteoarthritis of the knee

Wolff׳s Law suggests that the orientation of trabeculae in human bone changes in response to altered loading patterns. The aim of this study was to investigate trabecular orientation in both the femur and tibia and to compare this with the mechanical axis of the leg. The study involved analysis of radiographs from patients with osteoarthritis of the knee (n=91). For each patient, the trabecular orientation in both the distal femur and proximal tibia was measured from a standard anteroposterior radiograph of the knee and the mechanical axis of the leg was calculated from a long leg view taken while weight bearing. There was a significant correlation between the mechanical axis and the trabecular orientation in each of the regions considered in the femur (r=-0.41, -0.30, 0.52, and 0.23) and tibia (r=-0.27 and 0.31). Multiple regression analysis, with mechanical axis as the dependent variable, produced an R(2) of 0.62. Greater trabecular anisotropy (i.e. greater alignment) was observed in the medial femur and tibia compared to the lateral side (p<0.01). The results give an insight into the trabecular changes that may take place during development of osteoarthritis and following surgery. In particular, we propose that the orientation of the trabeculae in both the distal femur and proximal tibia will reflect the angle of mechanical loading through the knee.

Concepts in Computer Assisted Total Knee Replacement Surgery

Total knee arthroplasty (TKA) is commonly considered to be a reliable procedure, with implant survival rates higher than 90% at 10 to 15 years of follow-up. The goal of total knee replacement surgery is to relieve pain and obtain better knee function, those achieved by correct patient selection, pre-operative deformity, implant design, correct surgical technique and patient participation in the rehabilitation protocol (Nizard et al, 2002). Several technical requirements during TKA are important to obtain good results:  correction of deformities;  achievement of functional joint motion and stability;  optimal balancing of soft tissues;  satisfactory alignment in the frontal, sagittal and horizontal planes. From literature data alignment in frontal plane must be into 2o or 3o range around a neutral alignment; this thought is demonstrated by Ritter at al who observed that prostheses implanted in varus position had a lower survival rate than prostheses implanted in a neutral or valgus position (Ritter et al, 1994); moreover Jeffery at al observed that when mechanical axis was in 3o valgus-varus range, the loosening rate was 3%, whereas it’s 24% when the alignment was out of this range (Jeffery et al, 1991). The alignment in the horizontal plane is of particular importance for extensor mechanism stability, patellar wear, tilted patella, prostheses dislocation or loosening. In a study of Berger et al it was observed that patients with extensor mechanism problems have internal rotation of the femoral and tibial components (Berger et al, 1998). Technically, there is a definite relationship between the accuracy of implant positioning and long-term durability (Jeffery et al, 1991; Stulberg et al, 2002): the position of prosthetic components and, consequently the alignment of mechanical axis, could be the cause of polyethylene wear due to overload stresses, ending finally by prosthetic loosening. The postoperative mechanical axis of the lower limb should be a straight line passing through the center of the hip, the center of the knee, and the center of the ankle; so that satisfactory